Disclaimer: I do not own Sherlock or BBC or anything really... If I did I would have more money. Also, the quote of my title - "To Err is Human" - I didn't come up with that. Not my quote!

Summary: When one of Sherlock's plans to catch a criminal results in an injury, Sherlock realizes what John means to him and that he's been talking John for granted. Can Sherlock fix his mistakes? *Multi-Chapter* Not slash.

Rated T for some violence and mild swearing.

Author: Victoria

AN: I don't know how long it will take me to get new chapters up, but I will try to post regularly. Ideally, once a week for however long this story continues.

Chapter 1

Sherlock slunk along in the shadows, following John down the nearly empty road.

"It's 12 midnight and he's asking me to go get milk," John grumbled. "Couldn't he have picked a better time?"

The army doctor had no idea that Sherlock was following him, or why he was going to get milk at this time of night. Truth be told, this outing had nothing to do with milk at all. The past week had seen three murders, all by the same perpetrator, and Sherlock was getting close to discovering the murderer's identity. From the evidence he had analyzed, the consulting detective had deduced that the criminal would be searching for his next victim tonight and in this area of the city.

Sherlock also knew that on the way to the store for milk, John frequently took a short-cut through an alley that was perfect for an attempted murder.

The detective's plan was that the murderer would attack John - who, with his army experience, would easily fight him off. Sherlock would call Lestrade, and then he and John would hold down the murderer until the police arrived.

In his mind, the plan was faultless. It was for that reason that he hadn't told a single person his strategy, not even John. Besides, Lestrade and John always made takedowns so boring. Sherlock couldn't stand boring.

John hesitated at the entrance of the alleyway, considering the safety of walking into the darkened passageway. However, hurry and irritation won out over common sense - as Sherlock had known it would at this time of night.

"I just want to get this bloody errand over with. A half minute in an alleyway won't kill me," John grumbled, shoving his hands into his pockets as he entered the alley. Sherlock followed from a distance, almost giddy with anticipation. This was the highlight of his week.

A form shifted in the shadows of the far side of the alleyway. John peered into the darkness, then let out a yell as the murderer lunged at him.

The assailant raised a pistol, and John dove out of the way. Sherlock's breath caught in this throat. The murderer hadn't used a pistol before. He was not supposed to have a gun! The consulting detective fumbled with his phone, dialing Lestrade's number.

"Lestrade, get here right away!" Sherlock hissed into the phone. "We're in the alleyway near 221B - you know which one I mean!"

The murderer's finger tightened on the trigger as John tackled him, trying to get the gun away.

"Sherlock? What's going on?"

John and the assailant went down in a tangle of limbs. The gun fired with a bang, and the army doctor let out a cry of pain.

The consulting detective gasped, dropping his phone. John lay on the ground, clutching his leg in pain as the murderer stood up. Sherlock rushed out of the shadows and awkwardly swung a fist towards the criminal. The other man whirled on him, pistol-whipping him across the face. Sherlock crashed to the ground, blood dripping down his forehead.

John struggled to his knees, his eyes glazed with pain. He lunged for the gun in the murderer's hand, but missed and fell onto his side with a groan.

Sirens echoed nearby, and a lock of shock flashed through the criminal's eyes - a look that would have been mirrored in his face had it not been masked. Startled by the failed murder and the soon-arriving cops, he turned and fled down the alley, firing one last shot that glanced harmlessly off the brick wall.

One eye blinded by blood, Sherlock crawled over to his injured friend.

"Sherlock, what are you doing here?" John gasped out.

Wracked with guilt, the consulting detective didn't respond. He pressed both hands to the bullet wound in his friends upper leg. John let out a half-scream.

"Careful!" he rasped, almost passing out.

"Sherlock!" Lestrade's voice rang out as he ran into the alley. "What the hell happened here?"

"John's been shot," Sherlock stated breathlessly.

Lestrade nodded. "I heard the gunshot over the phone. An ambulance is on the way - for John and for you."

Donovan ran over and elbowed Sherlock out of the way, then aided John into a sitting position, speaking quietly to the wounded man.

"The murderer- he got away-" Sherlock grabbed Lestrade's arm to pull himself to his feet.

"The murderer? What?" The detective inspector took a moment to realize what his friend was talking about. When he did, his shoulders fell. "Oh no. Sherlock, you- you set this up? How could you?!"

"He wasn't supposed to have a gun!" Sherlock shouted. He buried his face in his hands. The ambulance screeched to a halt in front of the alleyway, and the paramedics rushed past the detectives with a stretcher.

Lestrade didn't reply. After a moment, he nudged Sherlock towards the ambulance. "You need medical attention too."

The consulting detective watched quietly as the paramedics lifted John's stretcher into the ambulance. "No. I'll take the Tube to the hospital," he said. He turned to leave, but was stopped by Lestrade's hand on his shoulder.

"At least let me drive you, if you won't take the ambulance," the other man offered.

Sherlock nodded reluctantly. "Fine. John- will John be alright?"

"From what I saw, I don't think the bullet hit an artery. Looks like he got lucky," Lestrade responded. "He should be fine."

The ambulance doors slammed shut, and the vehicle took off with its sirens wailing. Lestrade and Sherlock climbed into the detective inspector's car and followed the emergency vehicle.

Sherlock's head was throbbing, but the man barely noticed. His guilt and shock overwhelmed him, blotting out everything else. The plan had failed. One of his plans had failed, and John had gotten shot because of it.

"Dammit," the consulting detective murmured. Over and over, his thoughts returned to the look of pain on John's face. Sherlock's voice rose. "Dammit!" he shouted again. He slammed his fist down on the passenger side dashboard, leaving a smear of blood on the plastic. A mix of John's blood and of his own.

Lestrade didn't say a word. He just silently continued driving as Sherlock leant his head against the window and closed his eyes.